rule to replace vip ip with pool member

If you want to rewrite the TCP payload, I think you'd need to enable the stream filter in CLIENT_ACCEPTED. Enabling the stream filter in SERVER_CONNECTED only seems to allow you to rewrite the response from the server to LTM.

Normally, a load balancing decision isn't made until LB_SELECTED. However, you can force a load balancing decision in CLIENT_ACCEPTED using LB::select (Click here. You could then get the selected server IP using [LB::server addr].

  
 when CLIENT_ACCEPTED {  
  
     Make a load balancing decision 
    set lb_select [LB::select]  
  
     Now use the selection 
    eval $lb_select  
  
     Replace the virtual server IP with the selected pool member IP 
 STREAM::expression "@[IP::local_addr]@[LB::server addr]@"  
  
     Enable the stream filter 
    STREAM::enable  
  
    log local0. "Stream expression: @[IP::local_addr]@[LB::server addr]@"  
 }  
 

Aaron